Expedition 15:
Dark Life at Deep-sea Vents

Our Mission: Dark Life at Deep-sea Vents

In a series of video clips, co-principal investigators Stefan Sievert and Jeff Seewald describe their goals for Expedition 15, the new technology they’re using to gather samples in the deep ocean, and the scientific challenges they’ll face along the way. Launch interactive »

How Dive & Discover Can Help You and Your Students
Following a Dive & Discover expedition with your students helps you meet curriculum standards while giving your class a close-up look at real scientific research—all wrapped up in the adventure of an expedition on the high seas!
Find out more»

NEW Hot Topics!

Vent Ecosystems
The organisms that live at deep-sea hydrothermal vents seem strange and exotic, but the roles they play there are similar to the roles played by other species in ecosystems on land. Learn more »

Join Expedition 15 this winter as we venture into the Pacific Ocean to examine life in some of the most extreme environments on Earth—deep-sea hydrothermal vents.

These vents are like undersea geysers that form near volcanic hotspots on the ocean floor. They spit out a steady stream of hot liquid which can reach nearly 750 degrees Fahrenheit (400 degrees Celsius). Since these vents are more than a mile and a half below the surface, they are under enormous pressure—more than 3,500 pounds per square inch—and they are in total darkness. Yet in these seemingly hostile conditions, lush communities of life, from microbes to crabs to giant tubeworms, exist in the warm water next to the searing hot vents.

On our 14-day expedition, we’ll travel to the East Pacific Rise, a mid-ocean ridge about 600 miles south of Manzanillo, Mexico. There, we’ll examine the tiniest creatures in the vent communities’ food chain—single-celled organisms called bacteria and archaea. Organisms like these don’t usually exist in large numbers in the deep ocean, but at hydrothermal vents, they thrive. They become food for animals like shrimp and clams, which become food for even larger animals like fish and octopus. In this way, the microbes support the life of the entire community living around the vent, just as plants support ecosystems on land. But what, exactly, do the microbes live on?

Living without light

On land and near the surface of the sea, primary producers (plants and other organisms at the bottom of the food chain) get their energy from sunlight, through the process of photosynthesis. But sunlight isn’t available to organisms at deep-sea vents. Instead, they survive on inorganic chemicals and minerals dissolved in the hot hydrothermal vent fluids that bubble up from beneath the ocean floor. Using a process called chemosynthesis, the microbes convert those chemicals with redox reactions into energy they use to build their bodies. Those microbes form the base of the food chain at deep-sea vents, just like plants do on land.

Since the late 1970s, scientists have known that these microbes use chemosynthesis, but they haven’t yet discovered exactly how they do it. What sorts of microbes are down there, which chemicals are they using, and how fast are they growing? What role do these microbes play in the food web, both at the vents and in the rest of the deep ocean? During our cruise, a team of researchers will work in concert with the engineers and pilots who control the ROV (remotely operated vehicle) Jason. Together, they’ll deploy special equipment, including high-pressure samplers that will collect microbes and water from the vents. Those samples will help the researchers answer important questions: How do the microbes convert chemicals in the water into energy? How efficient are they at doing it? Which of their genes and enzymes are involved in the process? Have they developed symbiotic relationships with other bacteria at the vents?

Deep Science

Studying microbes from more than a mile below the surface can be a challenge. Some of the microbes live on the seafloor near the vents, but many live in between rocks below the seafloor, where they’re hard to reach. As a result, scientists don’t know much about their habitat, but they do know that they could play an important role in vent ecosystems.

The intense pressure at the seafloor here is also a problem for scientists. It can reach almost 3,600 pounds (1,600 kilograms) per square inch—the same pressure you’d feel if a hippopotamus was standing on your big toe. Since the microbes evolved to live in this high-pressure environment, bringing them up to the ship will affect their activities, and could even kill them.

The water itself would also be affected by the change in pressure. In the deep ocean, gases that the microbes need to survive are dissolved in the seawater, where the organisms can use them to create energy. Under much less pressure at the surface, those gases would bubble out of the water and escape.

Think of the samples like a bottle of soda. At high pressure, with the cap sealed, all the gas bubbles in the drink stay dissolved in the liquid, but as soon as you open the top, the pressure drops, letting the gases out (and causing a fizzy mess.) The same thing will happen to the gases inside deep-sea water samples unless they are kept under high pressure.

To get around these problems, the scientists will use Isobaric Gas-Tight samplers (IGTs). Isobaric means “same pressure.” These devices can suck in microbes and fluids and maintain them at the same deep-sea pressure as they come up to the surface.

Objectives

Once aboard the R/V (research vessel) Atlantis, we will set sail from Puntarenas, Costa Rica, and cruise west for four days to get to the vent sites. When we arrive, the Jason team will lower the vehicle a mile and a half down to the ocean floor, where it will hover near hydrothermal vents called “Crab Spa” and “Trick-or-Treat” to take samples of microbes, fluid, rocks, and animal life.

Since Jason is remotely operated, its team will be working 24 hours a day, and the vehicle will stay submerged for up to a week at a time. Using special underwater elevators, the team will send the IGTs and other samples back to the surface. While Jason continues to collect samples, scientists on the ship will start experiments on the samples already brought up.

Once the IGTs are on board, the scientists will try to grow the microbes (or bacteria and archaea) inside them. For the first time ever, they’ll be able to conduct experiments on living microbes in an environment that’s similar to their natural habitat: with the same water, chemicals, pressure, and other conditions they would experience at the bottom of the ocean. During these experiments, the scientists will be able to detect which chemicals the microbes use to survive. Through tiny pinhole valves in the IGT, they’ll add and subtract different chemicals from the water, testing the microbes’ metabolic rates, or how quickly and efficiently they “eat” those chemicals and convert them into biomass (the organic carbon and other substances that make up their bodies).

The researchers will also look at the DNA, RNA, and proteins of the microbes and bring samples of microbes back to shore for further study. If they can find which genes become activated and which enzymes are being produced to let the microbes “digest” the chemicals, they will be able to better understand how the process happens inside microbial cells. That will also give them clues to how the microbes settle down and grow at new vent sites, creating biofilms that form the foundation for vent communities.

Will the scientists be able to cast light on the mysteries that still surround dark life at vents? Come aboard with us on Expedition 15 as we visit some of the deepest, darkest ecosystems on Earth and get a glimpse into another world at the bottom of the ocean.